DESCRIPTION: (Applicant's abstract) The goal of this project is to determine the role of identified connections and specific glutamate receptors in the plasticity of adult motor cortex (MI) representations. The first hypothesis is that the forelimb/vibrissa border region contains overlapping distribution of output neurons to the spinal cord and facial nerve nucleus which could represent the anatomical basis for intracortical microstimulation (ICMS)-defected border shifts. Anterograde labelling from vibrissa cortex will be used to localize corticospinal terminations arising from vibrissa sites exhibiting a forelimb border shift. The second hypothesis is that the horizontal connections which cross between motor representations form an anatomical basis for rapid border shifts. A combination of ICMS and anterograde and retrograde tracer injections into the forelimb/vibrissa border region will be used to correlate the origin and topography of horizontal connections that cross map borders with respect to the location and limits of border shifts. This proposal will provide a comprehensive anatomical and functional basis of motor cortex plasticity which incorporates identified axonal pathways and specific glutamate receptor subunits.